Tagging is conducted in Biomark’s state-of-the-art self-contained custom tagging trailer. The tagging trailer is delivered and set up near the raceway or fish holding tank. AC power is usually provided by the hatchery power source (50 amps of 220 VAC). However, generator power can be provided. Water is normally pumped from a head box or directly from the raceway.

Water temperature is recorded as it enters the tagging trailer. Water temperature within the holding tank will be at ambient temperature and the re-circulated anesthetic water inside the tagging trailer is maintained to be within 0.5°C of the ambient water temperature. Fish are transported to the tagging trailer from the hatchery raceways in water-filled buckets and placed in a 500 gal freshwater holding tank inside the tagging trailer.

Coho tagging using the HPT12 PLT & MK25

Prior to tagging, fish are removed from the holding tank and placed in sinks containing anesthetic water. The total capacity of the anesthetic system (tank, sinks, troughs, hoses, and pipes) is approximately 100 gal. Anesthetic water is re-circulated through a 10-25 micron filter to remove particulate matter and an ultraviolet light filter for viral and bacterial disinfections. .The water contains MS-222 at a concentration of 45.0-50.0 mg/L. According to the manufacturer, these concentrations provide “moderately rapid anesthesia" and allow fish to be tagged within two minutes of being placed in an anesthetic sink. At this concentration, fish can be placed in the anesthetic for up to 30 minutes without risk of mortality.

Fish smaller than 60 mm fork length (FL) and fish displaying obvious signs of disease or injury are culled prior to tagging. Fish are also culled if they possess a tagging wound, but no tag is detected, due to the chance that a weak or damaged tag may have been implanted into the fish, which could interfere with a second implanted tag.

Tagging at Chief Joseph Dam

Fish are tagged with 12.5mm 134.2 kHz ISO PIT tags using a pre-loaded single use 12-gauge hypodermic needle (HPT12 PLT) fitted onto an implant device (MK-25). The trailer contains 4 tagging tables. Each table has a crew that consists of two taggers and one data collector (data collectors interrogate each tagged fish, measure their fork length using an electronic digitizing board, and note external signs of disease and injury). A full crew consists of approximately 14 persons.

Biomark staff pumping water from
the raceway to the tagging trailer

Fish are tagged using the techniques described in Prentice et al. (1990). This procedure involves piercing the body cavity at or near the ventral midline of a fish and inserting an RFID tag into the body cavity. Each fish is tagged at one of the four PIT-tag data collection stations where tag code, fish length, fish condition, weight (if required), and raceway number will be stored using PITTAG3 software (Pacific States Marine Fisheries Commission). Fish are then transferred from the tagging trailer to the holding raceway via a 3-inch diameter pipe.

Needles are used once and are collected for recycling at the end of the project. The tagging trailer and all equipment (pipes, pumps, aprons, nets, needles and implanters etc.) are washed with chlorinated water (1% solution) prior to departing the tagging site, and subsequently rinsed at the next tagging site or using a non-hatchery potable water source.

Our tagging rate averages between 4,000 and 6,000 fish per day at each tagging table (per 3 person crew). We normally tag 16,000 to 24,000 fish per day with all 4 tagging stations operating. If weights are required, the tagging rate will be reduced. Other factors effecting tagging rates are: cold water temperature, fish size (both small and large fish), and excessive sorting.